1. Field of the Invention
The present invention relates to a printing unit drive apparatus for a rotary press, and more particularly to a printing unit drive apparatus for a so-called shaft-less rotary press which includes at least one printing unit, folding units in a number not greater than the number of the printing units, and electric drive means provided for each of the printing and folding units, and in which the respective electric drive means are electrically connected to and controlled by a controller such that the respective electric drive means independently drive the respective printing and folding units in a synchronized manner.
2. Description of the Related Art
A rotary press which includes at least one printing unit and folding units in a number not greater than the number of the printing units is well known and is used, for example, as a rotary press for printing newspapers.
In such a rotary press, rotary portions of respective units must be rotated together in a state such that the rotational phase and the velocity of each rotary portion match those of other rotary portions.
For such a synchronized drive, in conventional techniques, a single main drive shaft is provided and is connected to a single or a plurality of electric drive means to be driven thereby; and rotation of the main drive shaft is transmitted to drive shafts provided for respective units via a gear train or the like. That is, by means of mechanical linkage among the respective units, the respective units are operated all together in a state such that the rotational phase and the velocity of each rotary portion match those of other rotary portions.
However, since such a mechanical linkage mechanism requires a large number of parts and is complicated and large, manufacturing costs increases, and its operation, maintenance, and management are troublesome. In order to overcome the above-described drawbacks, there has been proposed a so-called shaft-less rotary press. In the shaft-less rotary press, at lease one electric drive means is provided for each of printing and folding units; the respective electric drive means of the units are rotated together while being electrically synchronized; and the rotational phase and speed of each rotary portion are controlled electrically. Thus, the respective units are operated in a mutually matching manner. Such a shaft-less rotary press is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 8-34108, 8-85196, and 8-103996.
Japanese Patent Application Laid-Open No. 8-34108 discloses a printing unit drive apparatus in which the shaft of one plate cylinder and the shaft of one blanket cylinder are connected via gears for interlocked operation, and these cylinders serving as a driven portion are driven by a single electric drive means. Further, as a preferred embodiment, there is described in detail a drive apparatus in which the rotor shaft of the electric drive means and the journal of one of the cylinders serving as a driven portion are disposed such that their axes become parallel to each other and perpendicular to the frame of the printing unit, and the rotor shaft of the electric drive means and the journal of one of the cylinders are connected via a transmission mechanism including a timing belt and timing belt pulleys.
Japanese Patent Application Laid-Open No. 8-85196 discloses a printing unit drive apparatus for a printing unit which includes a combination of a plate cylinder and a blanket cylinder, or a combination of a plate cylinder, a blanket cylinder, and an impression cylinder. In the drive apparatus, one to all of the cylinders of the printing unit serve as a driven portion, and an appropriate cylinder of the driven portion is connected directly to electric drive means to be driven thereby, and the cylinder and the remaining cylinders are connected via gears for interlocked operation.
Further, as a preferred embodiment, there is described in detail a mechanism for fixing the rotor shaft of the electric drive means to the journal of the cylinder, as well as a drive mechanism for fixing the tip end of the rotor shaft of the electric drive means to the side end portion of the cylinder in order to use the rotor shaft of the electric drive means as the journal of the cylinder.
Japanese Patent Application Laid-Open No. 8-103996 discloses a printing unit drive apparatus in which a single or a plurality of rotatable functional components (e.g., a driven component such as a blanket cylinder) is/are connected directly and securely to electric drive means. Further, as a preferred embodiment, there is described in detail a drive apparatus in which, in order to establish direct and secure connection between the electric drive means and an appropriate cylinder serving as a driven portion, there is employed a connection mechanism such that the end shaft of the cylinder is extended into the electric drive means and a rotor is attached thereto, whereby the end shaft of the cylinder is used as the rotor shaft of the electric drive means.
The above-described conventional drive apparatuses have the following drawbacks.
First, all of the drive apparatuses disclosed in the three publications lack braking means, because they are designed based on the consideration that during operation printing units can be braked through electrical control of the electric drive means. However, in such a braking scheme, there is not taken into account stoppage of the printing units that occurs when supply of electricity to the electric drive means is shut off, for example, at the time of power failure.
That is, in the conventional drive apparatuses, when supply of electricity to the electric drive means is shut off, control of the electric drive means becomes impossible, and driven portions of the respective printing units continue their rotation, due to inertial force, in an uncontrolled state. Therefore, each driven portion starts to rotate independently of other driven portions, and there arise accidents such that the tension acting on paper web--which is caused to travel by means of rotation of the driven portions--changes at longitudinal positions, resulting in rupture of the paper web and such that ruptured paper web winds around a rotating driven portion (e.g., blanket cylinder).
Further, in the drive apparatus disclosed in Japanese Patent Application Laid-Open No. 8-34108 and having a transmission mechanism composed of a timing belt and timing belt pulleys, in order to transmit a desired drive force, there must be taken either or both of the following measures: (1) increasing the distance between the timing belt pulleys in order to increase the contact angle between the timing belt and the timing belt pulleys; and (2) increasing the face width of the timing belt pulleys and the timing belt. Therefore, a large space is required for installation of the drive apparatus.
In addition, in the drive apparatus disclosed in Japanese Patent Application Laid-Open No. 8-34108, since the timing belt is caused to travel at high speed, the timing belt disturbs the surrounding air to sometimes generate high-pitched noise, thereby deteriorating the working environment.
Moreover, in the drive apparatus, since the rotor shaft of the electric drive means and the end shaft of the driven portion are disposed such that their axes become parallel to each other and perpendicular to the frame of the printing unit, the amount of projection of the printing unit in the direction perpendicular to the frame surface increases, so that the printing unit occupies a relatively large space in the direction perpendicular to the frame.
Meanwhile, in the drive apparatuses disclosed in Japanese Patent Application Laid-Open Nos. 8-85196 and 8-103996, the rotor shaft of the electric drive means and the end shaft of the driven portion are directly connected with each other, and thus there is overcome the drawback of the above-described drive apparatus equipped with a timing-belt type transmission mechanism. However, since no reduction mechanism is disposed between the rotor shaft of the electric drive means and the end shaft of the driven portion, it becomes necessary to use electric drive means that can output a large torque, resulting in an increase in size of the electric drive means. In order to cope with this new problem of an increase in the size of the electric drive means to thereby reduce the size of the electric drive means, there is employed a structure in which only one cylinder among a plate cylinder, a blanket cylinder, and an impression cylinder is selected as a driven portion that is driven by a single electric drive means, or there is employed a special electric drive means in which a common shaft is used as the end shaft of the driven portion and the rotor shaft of the electric drive means.
However, in the case where only one cylinder is driven by a single electric drive means, each printing unit requires a plurality of electric drive means whose number is not less than the number of the cylinders; i.e., three to nine electric drive means. In addition, more complicated control means is required in order to rotate all the respective cylinders together at the same speed while matching their rotational phase to each other. Further, failures and malfunctions occur more frequently, and maintenance and inspection become troublesome. Moreover, in a so-called divided plate cylinder which has a width corresponding to four pages of newsprint and whose circumferential surface is axially divided into two surfaces, which are to be driven separately, two electric drive means are required for one plate cylinder. Therefore, the above-described drawbacks become more remarkable.
Further, since the electric drive means is directly connected to the driven portion, the electric drive means must be operated in a relatively low efficient state in order to rotate the driven portion at a desired speed (e.g., 625 rpm) for steady printing operation. In addition, when the above-described special electric drive means is used, costs increase, and in view of failure and repair, special parts must be stocked. Moreover, work for repair and part replacement requires accuracy, which in turn requires experience.
Moreover, in the drive apparatuses disclosed in Japanese Patent Application Laid-Open Nos. 8-85196 and 8-103996, since the rotor shaft of the electric drive means and the end shaft of the driven portion are disposed such that their axes become coaxial with each other and perpendicular to the frame of the printing unit, the amount of projection of the printing unit in the direction perpendicular to the frame surface increases, so that the printing unit occupies a relatively large space in the direction perpendicular to the frame.